Crowds are usually capped at 80,000 for transport network capacity reasons but an attendance of 90,000 is expected for the contest in which Joshua's IBF title and the vacant WBA Super and IBO heavyweight belts are up for grabs.
It would match the record 90,000 attendance for the Len Harvey versus Jock McAvoy bout at London's White City in 1939.
"(London Mayor) Sadiq (Khan) urged me to bring the biggest fights to the city and I'm delighted to have the biggest fight in British boxing history at Wembley," Eddie Hearn told the BBC.
